Recently manufactured vehicles are equipped with a special system called On-Board Diagnostic II (OBD II). OBD II monitors all engine and drive train sensors and actuators for shorts, open circuits, lazy sensors and out-of-range values as well as values that do not logically fit with other power train data. Thus, OBD II keeps track of all of the components responsible for emissions and when one of them malfunctions, it signals the vehicle owner by illuminating a Malfunction Indicator Lamp (MIL), such as a check engine indicator. It also stores Diagnostic Trouble Codes (DTCs) designed to help a technician find and repair the emission related problem. OBD II also specifies the means for communicating diagnostic information to equipment used in diagnosing, repairing and testing the vehicle.
An illuminated MIL means that the OBD II system has detected a problem that may cause increased emissions. A blinking MIL indicates a severe engine misfire that can damage the catalytic converter. The MIL is reserved for emission control and monitored systems and may not be used for any other purpose. The “Check Engine,” “Service Engine Soon” or other “engine symbol” message is typically used as a MIL indicator.
The Clean Air Act of 1990 requires inspection and maintenance (I/M) programs to incorporate OBD II testing as part of a vehicle's emissions inspection program. When fully implemented, 1996 and newer model year vehicles registered in a required emission test area must be tested annually. If DTCs are present, or the diagnostic monitor software has not adequately tested the vehicle's emission control systems, the vehicle fails the emissions test. Otherwise, the vehicle passes the emissions test.
In order for a vehicle to pass the OBD II emissions tests, the vehicle under test (VUT) must report that all pertinent (as defined by each state) diagnostic monitors have completed their tests of the vehicle system. Diagnostic monitors that have completed their tests are said to be in a “Ready” state. Diagnostic monitors that have not completed their tests are said to be in a “Not Ready” state. Checking the readiness state of the diagnostic monitors via OBD II was incorporated into emissions testing to prevent owners from attempting to pass vehicles not in compliance by simply clearing the vehicle's Diagnostic Trouble Codes and then quickly retesting the vehicle before the root problem was again detected by the vehicle's on board computer. Clearing the DTCs on a vehicle also sets all of the monitors to the “Not Ready” state. Until the vehicle has been driven under the proper conditions for all of the monitors to execute their tests, the vehicle will not be ready for an emissions test.
The readiness state of the diagnostic monitors of the OBD II system indicates that emission system components have been checked. If a particular monitor is set to “Ready,” the monitor has checked its assigned components and systems. If a problem is found, a DTC is set, and a technician can retrieve the code. When all of the monitors supported on a vehicle are “Ready,” the vehicle is ready for an emissions test.
Unlike DTCs, the readiness state of the diagnostic monitors cannot be manipulated via a scan tool, rather their status is altered by a Drive Cycle, which is a series of specific vehicle operating conditions that enable the diagnostic monitors to test the vehicle's emissions control hardware. As each monitor completes its testing, its readiness state will be set to “Ready.” An example of a simple Drive Cycle is where the vehicle's engine is started, and the vehicle is driven for seven minutes. Then the vehicle is driven in stop-and-go traffic for six minutes including one minute of idling. After which, the vehicle is accelerated to forty-five miles per hour and maintained at that speed for one minute.
Repair shops and drivers may not be aware of when the vehicle is “Ready” to be tested for emissions, or when the required Drive Cycle has been completed in order to properly test the vehicle's emissions. Therefore, repair facilities need an inexpensive tool that enables either an untrained personnel (such as a driver) or a trained repair facility personnel, to determine the status of the OBD II readiness state of the diagnostic monitors while operating the vehicle through normal driving conditions. In addition, repair facilities need to encourage their client to return to their shop after the readiness monitors have been reset to the “Ready” position in order to verify the repair and/or complete the emissions testing.
When the tool is plugged into the vehicle, it will start to interrogate the vehicle's diagnostic systems at a set interval. This set interval, however, may interfere with the vehicle's diagnostic system tests and not allow the tests to proceed. Thus, the tool may not be able to retrieve the data that it needs to complete its own test as the vehicle can not complete its own tests.
Accordingly, a tool is desired that can interrogate a vehicle without interfering with the vehicle's own diagnostic system tests. The tool should be able to adapt and change the interval time in which it interrogates or communicates with the vehicle.